For traditional radiotherapy device, usually there has a relative movement between the body of patient and the radioactive sources. For one example, in therapy, when patient lying on the operating-table, the ray source of the radiotherapy device relatively moves around with the table, then different body part of the patient be radiated; in another example, the patient lying fixedly on the operating-table, and the table makes relative movement to the ray source, then different body part of the patient be radiated also. Nevertheless, the relative movement between the ray source and the body of the patient may cause some physical contact or collision, thus harmful to the patient.
Some radiotherapy devices already have protectors, but these protectors are with complicated structure and high cost, using the devices with such protectors for treatment will heave the economic burden on the patients.